The castle is surrounded by a moat on all sides, except the northern section, which was bordering the sea and can be accessed from the bridge and the gate on the southern side. It is mainly composed of the Aragon walls and the main Hohenstaufen tower, and is currently used for exhibitions.

According to the tradition, in 1221 Emperor Frederick II met St. Francis of Assisi in this castle. According to tradition, the emperor had a courtesan sent to Francis's room and watched through a peephole to see what would happen. When Francis sent the woman away, Frederick was impressed with his principles; the two spent the rest of the night in conversation. This story is not confirmed beyond doubt, but it is considered believable.[1]